This invention relates generally to earth working and snow removal equipment, and has particular reference to a novel operating and shock cylinder assembly for vehicle mounted scraper blades and the like.
Vehicle mounted underbody blades for scraping, grading and snow removal generally employ hydraulic cylinders for pivoting the blades between retracted and road engaging positions. Since the blades frequently encounter non-yielding obstacles, they must be provided with yield or trip means so that the blades or their associated mechanisms are not damaged. In the prior art, the blade yield means has most commonly consisted of compression spring assemblies positioned between the operating cylinders and blade.
A more compact and effective shock absorbing and tripping mechanism is disclosed in U.S. Pat. No. 3,893,518 granted July 8, 1975 to the applicant herein. In that patent, which represents the closest prior art known to the applicant, the spring means are incorporated in the interiors of the operating cylinders thereby saving space and obviating the need for locating the springs, along with their attachment and guide means, in an exposed position on the blades.
A problem has, however, been encountered with the mechanism disclosed in the patent cited which problem is human rather than mechanical. Thus, in the patented shock absorbing cylinders, it is possible to increase the oil pressure enough so that the springs in the cylinders become non-resilient solid masses and the cylinders lose all shock absorbing and tripping capabilities. Unfortunately, this has happened due to inadvertence or carelessness.